The present invention relates to an optical switch for switching connections of optical signals transmitted through a plurality of optical fibers, and more particularly to a three-dimensional optical matrix switch which employs mirrors for controlling the direction of each optical beam signal.
In fiber-based optical communications, an N×N optical switch is employed for connecting arbitrary one of optical signals transmitted to N input ports through optical fibers to one of N output ports. The optical switch can change over these connections.
U.S. Pat. No. 6,347,167 describes a three-dimensional optical matrix switch which uses a fiber collimator array and a mirror array to form optical paths.
The three-dimensional optical matrix switch described in U.S. Pat. No. 6,347,167 comprises a housing in which fibers and collimator lenses are arranged; a substrate on which input micromirrors and output micromirrors are arranged on the same surface; and a cap formed with a reflecting surface. These components are arranged in parallel with one another. A beam exiting from a lens transmits the substrate, reflects on the reflecting surface of the cap, and reflects on one of the input micromirrors. Then, the beam is emitted from the cap. The beam is further folded back by a reflection on a second cap, reflects on one of the output micromirrors, and couples to an output fiber through a path similar to the input side.
However, since the optical matrix switch described in U.S. Pat. No. 6,347,167 must provide a beam passing region on the surface on which the mirrors are arranged, the mirrors are packed at a lower density. Due to limitations in an optical path length between input and output fibers (working distance) and a maximally deflectable angle of the mirrors, a reduction in the mirror packing density results in a less number of channels which can be coupled by the optical matrix switch.